Poly(arylene sulfide) polymers

ABSTRACT

Improvement in processing and coating quality of poly(arylene sulfide) is achieved by incorporating therewith a sulfurcontaining compound of the formula   IN WHICH NOT MORE THAN FOUR OF THE POSITIONS OCCUPIED BY R1-R6 contain hydrogen, from 1 to 3 of the positions occupied by R1-R6 have a substituent R&#39;&#39;SH group in which R&#39;&#39; is an alkylene radical of 1 to 3 carbon atoms and from 0 to 5 of the positions occupied by R1-R6 are filled by alkyl groups having 1 to 12 carbon atoms.

United States Patent [191 Tieszen POLY(ARYLENE SULFIDE) POLYMERS [75] Inventor: Dale 0. Tieszen, Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

22 Filed: Sept. 19,1973

21 App]. No.: 398,573

[52] U.S. Cl. 260/79, 117/124 R, 117/132 R, 117/161 R, 260/33.4 R, 260/37 R, 260/79.1,

[51] Int. Cl C08g 25/00 [58] Field of Search .[260/79, 79.1; 117/161 R, 117/132 R, 124 R [56] References Cited UNITED STATES PATENTS 3,386,950 6/1968 Horvath et a1 260/45.7 S

Primary Examiner-Melvyn I. Marquis Attorney, Agent, or Firm-Neuman, Williams, Anderson & Olson Dec. 10, 1974 [57] ABSTRACT Improvement in processing and coating quality of poly(arylene sulfide) is achieved by incorporating therewith a sulfur-containing compound of the formula 9 Claims, N0 Drawings POLY(ARYLENE SULFIDE) POLYMERS This invention relates to improved coating compositions containingpoly(arylene sulfide) polymers.

It is known that poly(arylene sulfide) polymers are useful as coating materials, since coatings formed thereof are strong, heat stable and resistant to most industrial chemicals and fumes. Thus, for example, poly- (arylene sulfide) polymers can be advantageously employed as coatings for metals such as steel, aluminum,

nickel, brass, copper, as well as ceramics, glass and other substrates stable at the curing temperaturerequired for the coating, i.e., 600750 F.

It is an object of this invention to provide coating compositions comprising poly(arylene sulfide) polymers having enhanced properties as to processability, adherency and coating flexibility.

It is a further object of this invention to provide poly- (arylene sulfide) coating compositions which canbe cured at a relatively fast rate to form good, adherent, flexible coatings for metals and other materials.

The above and other objects of this invention are achieved by incorporating with poly(arylene sulfide) polymers a minor amount of certain relatively high molecular weight thiol compounds. The use of thiols or polythiols with poly(arylene sulfide) resins is disclosed in US. Pat. No. 3,386,950. That patent discloses that thiols and polythiols broadly can be employed to reduce or prevent discoloration of poly(arylene sulfide) resins. In accordance with this invention, it has been found that certain thiol compounds can be effectively incorporated in poly(arylene sulfide) resins to speed up the cure rate thereof and improve the quality of the coatings formed by the polymers.

The thiol compounds which have been found useful in accordance with this invention can be represented by the formula:

s- R-g Bax Rx I l.

in which not more than four of the R positions contain hydrogen, from 1 to 3 of the R positions have a substituent RSH group in which R is an alkylene radical of l to 3 carbon atoms and from to 5 of the R positions are filled by alkyl groups having 1 to 12 carbon atoms.

Representative thiol compounds are dodecylbenzyl mercaptan; 1,2-di-mercaptomethyl benzene; 1,3- dimercaptomethyl benzene; (l-mercapto)propyl-2- methylbenzene; l,3dimercaptomethyl-4-ethyl benzene; l-(2 mercapto)ethyl-3,4-dimethylbenzene; l-mercaptomethyl-4-octyl benzene; a,a'-xylene dithiol; l-(Z-mercapto-ethyl)-4-i-propyl benzene; l,3,5-tri-mercaptomethyl benzene and mixtures thereof.

The sulfur-containing compounds are incorporated in poly(arylene sulfide) resins prior to curing in amounts ranging from about 3 to l0 parts or more by weight of the polymer.

The above compounds are used in accordance with this invention with normally solid poly(arylene sulfides) generally, regardless of the method of their preparation. Thus, they may be used, for example, with poly(arylene sulfide) resins prepared as described in US. Pat. No. 2,513,188, wherein polyhalo aromatic compounds are reacted with sulfur and a metal sulfide at fusion temperatures. They can also be used with resins manufactured by the method described in British Pat. No. 962,941, wherein metal salts of halothiolphenols are heated at a polymerizing temperature. Likewise, the specified thiol additives are useful to improve the coating properties of normally solid poly(arylene sulfide) polymers as described in US. Pat. No. 3,354,129 which issued Nov. 21, 1967 to Edmonds and Hill. As

disclosed in that patent, these polymers can be pre pared by reacting a polyhalo-substituted aromatic compound containing unsaturation between adjacent ring atoms and a mixture made by contacting an alkali metal sulfide with a polar organic compound. The resulting polymer contains the cyclic structure of the polyhalo-substituted compound coupled in repeating units through a sulfur atom. Because of their high thermal stability and availability of the materials from which they are prepared, preferred polymers are those having the repeating unit RS where R is phenylene, biphenylene, naphthylene, biphenylene ether or a lower alkyl-substituted derivative thereof. By lower alkyl is meant alkyl groups having 1 to 6 carbon atoms such as methyl, propyl, isopropyl, n-hexyl and the like.

The solid poly(arylene sulfide) polymers can have varying meltingtemperatures, such as in the range from 400 to 900 F. Polymers of phenylene sulfide nonnally have melting temperatures in the range of about 550 to 900 F. The preferred polymers have an inherent viscosity in chloronaphthalene at 206 C. of at least 0.1, preferably between 0.1 and 0.3, more preferably between 0.13 and 0.23. A particularly preferred polymer is poly(phenylene sulfide) (PPS), having a melt flow of 50 to above 2,500 (limit of instrument measurement by ASTM D-l238- modified to operate at a temperature of 343 C under a 5 kg. total load with melt flow rate reported in grams/ 1 0 minutes. The virgin PPS which has a melt flow of above 2,500 can be precured by heating in air at 500520 F. for 1-6 hours to lower the original melt flow.

The thiol additives of this invention can be incorporated in the polymer prior to curing in any convenient manner. Thus, for example, the additives can be added as such to the polymer and the resulting mixture can be agitated in any convenient manner to achieve good mixing. A particularly convenient manner of introducing the additives into the polymer is the addition of the thiol dissolved in a volatile solvent such as hexane, benzene, acetone and the like with subsequent volatilization of the solvent.

The term curing as used herein means a heat treatment of the polymers wherein the melt flow of the polymer is decreased from a value above 2,500 to essentially a value below about or even to 0. The curing times and temperatures for a particular poly(arylene sulfide) polymer will vary widely, but can be readily determined by subjecting the polymer to a heat treatment in air at 510 F. for periods varying from 5% to 6 hours and measuring, at intervals, the melt flow of the polymer using ASTM D-l238-70 modified to operate at a temperature of 343 C. under a 5 kg. total load with melt flow rate reported in grams/l0 minutes.

The use of the said thiol additives of this invention speeds up the cure rate of either slow curing or fast curing resins with the improvement in cure rates being evidenced by increased flexibility of the coating. For example, a slow curing poly(phenylene sulfide) resin will ordinarily require 6 hours at 510 F. in air curing time to have a melt flow of less than about 400 without accelerators (see Table II). A fast curing poly(phenylene sulfide) resin will cure to a melt flow of less than about 400 in 2-4 hours at 510 F. Very fast curing resins will cure to a melt flow of less than 100 in l2 hours at 510 F. in air without additives. Thus, a polymer with a slow cure rate, which would be reflected in a poorer coating test rating, can be made more suitable for coating with the use of these additives. Also, a polymer having a very good coating test rating can be cured in less time with the use of the described additives than would be required without these additives. It is desirable to accelerate the cure rate of a poly(phenylene sulfide) coating on a substrate, especially certain metals, such as carbon steel, in order to shorten the time such metals have to be exposed to the high curing temperature of say 700 F. In fabricating pipe, for example, the exposure of these to long periods of high temperatures is undesirable because they have a tendency to embrittlement, yet a polymer coating may be required to protect such metal surfaces from corrosion. These mercaptan additives materially shorten the required exposure time of the substrates to these high temperatures as shown below.

In addition to the mercaptan additives, the compositions of this invention can contain other ingredients conventionally employed in poly(arylene sulfide) coating compositions such as, for example, fillers such as titanium dioxide, calcium carbonate, aluminum oxide, aluminum silicate, pigments, resins and/or plasticizers, ferric oxide, silicon dioxide, asbestos fibers. glass f1- bers, poly(tetrafluoroethylene) and the like.

The advantages of the invention will be further illustrated by the following specific examples.

EXAMPLE I A coating composition was prepared by mixing in a blender 3 parts by weight of poly(phenylene sulfide) polymer, 1 part of titanium dioxide as a filler and 6 parts of propylene glycol as a vehicle. The poly(phenylene sulfide) polymer employed was made according to Example 1 of U.S. Pat. No. 3,354,129 referred to above and is characterized by a melt flow above 2,500, density 1.34 and intrinsic viscosity 0. l5; a slow curing resin, i.e., a curing time of about 6 hours in air at 5 10 F. to reduce the melt flow to below about 400 without accelerators.

To the above mix were added various amounts of various sulfur compounds dissolved in isopropanol. The formulations were subjected to a coating test which involved the following:

COATING TEST PROCEDURE 1. Cold rolled steel panels, 3 inches X 6 inches X 0.035 inches, were degreased and heated in a gas- 0 flame to a blue-gray color.

2. After cooling to room temperature, three coats of the formulation were applied successively with a No. 60 coating rod, and each coat was baked at 700 F. for 30 minutes (or less as noted in Tables I] and III).

3. After the third coat bake, the coated panel was annealed for 2 hours at 450 F. and then allowed to stand overnight at room temperature.

4. The coated panels were bent over a 3/16 inch D mandrel. and the elongated portion was examined with the aid ofa microscope at 20X magnification. The ratings of l to 5 correspond to the following observations:

Rating Observations I No cracking on elongated portion of the annealed coating.

2 Occasional microcracks along elongated coating.

3 Numerous microcracks and some cracking which may he barely visible to the unaided eye.

4 Cracks are continuous and easily visible Complete rupture of the coating.

The results of the coating test were as follows:

TABLE I EFFECT OF SULFUR COMPOUNDS AND SODIUM HYDROXIDF. ON COATING TEST This example illustrates the effect of the additives of the invention on melt flow numbers of a poly(phenylene sulfide) polymer (PPS) which is a slow curing resin which was cured for 6 hours at a temperature of 510 F. Titanium dioxide as a filler and propylene glycol as a vehicle were used as in Example I. Table [I gives the results. The precure melt flow of the resin was above 2,500.

TABLE II EFFECT OF ADDlTlVES ON 510 F CURE OF SLOW CURE PPS ON MELT FLOW NUMBERS Method Wt. of Mixing Compound of PPS MFN Additive None 373 Manual Dodecylbenzyl mereaptan 5 0 do. a.a'-p-xylene dithiol 5 29.] do. Sulfur S 1 14 do The MEN :5 ag/lt] min. at 650 F wilh a 5 Kg weight after the material was cured at 5 HP F16 hours. (ASTM 042N modified to operate at a temperature of 343 C. under a 5 kg. total load with well flow rate reported in grams/l0 minutes The data illustrate the accelerating effect of the addiweight of said sulfide a sulfur-containing compound of tives in modifying the melt flow of the virgin resin. the formula EXAMPLE III m This example illustrates the effect of the additives of v 5 A the invention on improvement of coating quality for two lots of poly(phenylene sulfide) polymers (PPS). PPS Lot 1 is a slow curing polymer which, when cured T for 30 minutes at 700 F., has a coating rating of l or 2. PPS Lot 2 is a faster curing resin which, when cured for minutes at 700 F., has a coating rating of 1 The coating compositions contained titanium dioxide as a filler and propylene glycol as a vehicle as in Example I. The results are shown in Table III.

in which not more than four of the positions occupied by R R contain hydrogen, from 1 to 3 of the positions occupied by R,R have a substituent R'SH group in TABLE III EFFECT OF ADDlTlVES ON COATING TESTS WITH SHORTER CURE TIMES AT 700 F.

The data demOnStfate that, With the additive, eXCel- 30 which R is an alkylene radical of l to 3 carbon atoms lent coatings can be obtained with considerably shortd f 0 t 5 f th iti i d by R, R are ened Cur PC filled by alkyl groups having 1 to 12 carbon atoms.

Those modlficanons and equwalems Whlch fall 5. A method in accordance with claim 4 wherein the the Of the invention are to be: Considered u]fur containing compound is dodecylbenzyl mercup a part thereof tan,

What is claimed is:

l. A method of coating which comprises applying to an article to be coated a composition comprising a poly( arylene sulfide) polymer and from about 3 to 10 percent by weight of said polymer, a sulfur-containing 40 compound of the formula compound is a,a'-xylene dithiolv lene sulfide) resin which comprises incorporating therewith in an amount from about 3 to 10 percent by weight of said resin, a sulfur-containing compound of v the formula in which not more than four of the positions occupied by R -R contain hydrogen, from 1 to 3 of the positions Occupied y ie have a Substitllenl g p in in which not more than four of the positions occupied which R is an alkylene radical of l to 3 carbon atoms by R -R contain hydrogen, from 1 to 3 of the positions and from 0 to 5 of the positions occupied by R R are upied by R R have a substituent R'SH group in filled by alkyl groups having 1 to 12 Carbon atOmS- which R is an alkylene radical of l to 3 carbon atoms 2. A method in accordance with claim 1 wherein the and from 0 to 5 of the positions occupied by R R are sulfur-containing compound is dodecylbenzyl mercapfilled by alkyl groups having 1 to 12 carbon atoms. tan. 8. A method in accordance with claim 7 wherein the 3. A method in accordance with claim 1 wherein the sulfur-containing compound is dodecylbenzyl mercapsulfur-containing compound is a,a'-xylene dithiolr t 4. A method of coating which comprises applying to 9. A method in accordance with claim 7 wherein the an article to be coated a composition comprising poly(- sulfur-containing compound is a,a'-xylene dithiol. phenylene sulfide) and from about 3 to 10 percent by 6. A method in accordance with claim 4 wherein the 7. A method of reducing the melt flow of a poly(a'ry- 

1. A METHOD OF COATING WHICH COMPRISES APPLYING TO AN ARTICLES TO BE COATED A COMPOSITION COMPRISING A POLY(ARYLENE SULFIDE) POLYMER AND FROM ABOUT 3 TO 10 PERCENT BY WEIGHT OF SAID POLYMER, A SULFUR-CONTAINING COMPOUND OF THE FORMULA
 2. A method in accordance with claim 1 wherein the sulfur-containing compound is dodecylbenzyl mercaptan.
 3. A method in accordance with claim 1 wherein the sulfur-containing compound is Alpha , Alpha ''-xylene dithiol.
 4. A method of coating which comprises applying to an article to be coated a composition comprising poly(phenylene sulfide) and from about 3 to 10 percent by weight of said sulfide a sulfur-containing compound of the formula
 5. A method in accordance with claim 4 wherein the sulfur-containing compound is dodecylbenzyl mercaptan.
 6. A method in accordance with claim 4 wherein the compound is Alpha , Alpha ''-xylene dithiol.
 7. A method of reducing the melt flow of a poly(arylene sulfide) resin which comprises incorporating therewith in an amount from about 3 to 10 percent by weight of said resin, a sulfur-containing compound of the formula
 8. A method in accordance with claim 7 wherein the sulfur-containing compound is dodecylbenzyl mercaptan.
 9. A method in accordance with claim 7 wherein the sulfur-containing compound is Alpha , Alpha ''-xylene dithiol. 